1. Field of the Invention
This invention relates to valuable alkylated aromatic hydrocarbons. In one aspect, this invention relates to a method of producing said hydrocarbons from otherwise marginally valuable tar obtained from the reaction product of an alkylation process comprising contacting benzene and/or toluene with a C.sub.2 -C.sub.3 olefin. In another aspect, this invention relates to said method wherein the tar is contacted with benzene and/or toluene in the presence of a crystalline aluminosilicate molecular sieve catalyst.
2. Description of the Prior Art
The reaction product produced by the alkylation of benzene and/or toluene with ethylene and/or propylene (in the presence of an alkylation catalyst and at alkylation parameters) comprises both valuable alkylated aromatics, such as ethylbenzene, ethyltoluene, cumene, etc., and tar. This tar is a problem in as much as it represents lost alkylated aromatic hydrocarbons. The size of this problem, of course, is dependent upon the amount of tar that can be converted to the alkylated aromatic hydrocarbons. The more tar that can be converted, the smaller the size of the problem. Presently, only the tar fraction that distills below about 240.degree. C is considered convertible while the remaining tar fraction is not so considered (and is thus generally burned as fuel, a marginally valuable utility). Accordingly, the aforementioned alkylation processes are generally conducted in such a manner as to minimize this latter tar fraction. This equates with conducting the alkylations at an olefin:aromatic mole ratio of substantially less than 1 which results in a large amount of unreacted aromatic being present in the resulting reaction product. The unreacted aromatic must then be removed from the reaction product and eventually recycled. This all translates into a less efficient and more expensive alkylation process than a similar process wherein the tar fraction above about 240.degree. C is convertible. It is therefore desirable to have a method for converting the tar fraction above about 240.degree. C to valuable alkylated aromatic hydrocarbons.